| Trinet Corporation | Tokyo |
| Tripwire Japan Co., Ltd | Tokyo |
| True Data Co., Ltd | Tokyo |
| Truss Co., Ltd | Tokyo |
| Trust Technology Co., Ltd | Tokyo |
| Trust Technology Corporation | Tokyo |
| Trustec, Inc. | Tokyo |
| TrustHub K.K. | |
| TSP Co., Ltd | Tokyo |
| Tsubaki Studio | |
| Tsuda University | |
| Tsugi GK | Niigata |
| Tsukuba Engineering Co., Ltd | Tokyo |
| Tsukuba University of Technology | |
| Tsukumo | Tokyo |
| Tsukuzi Software Co., Ltd | Tokyo |
| Tsunagu.AI, Inc. | |
| Tsuru Capital | |
| Tsuru University | |
| Tsuruga City Nursing University | |
| Tsurumi University & Tsurumi Junior College | |
| Tsuruoka National College of Technology | |
| Tsuzuki Denki Co., Ltd | Tokyo |
| Turbo Systems Co., Ltd | Tokyo |
| Turn and Frontier Co., Ltd | Tokyo |
| TWOTOP | Osaka |
| Tyrell Systems Co., Ltd | Tokyo |
| U-netSURF | Tokyo |
| Ube Frontier College | |
| Ube Frontier University | |
| Ubie Co., Ltd | Tokyo |
| Ubiquitous Technologies, Inc. | Tokyo |
| UBIS Co., Ltd | Tokyo |
| Ubuntu Japanese Team | Tokyo |
| UEDA Cable Vision Corporation | Nagano |
| Ueno Seiki Co., Ltd | Fukuoka |
| Uhuru Corporation | Tokyo |
| UI Group | Tokyo |
| Ultimate Graphics Co., Ltd | Tokyo |
| Ultinet Co., Ltd | Tokyo |
| ULURU Co., Ltd | Tokyo |
| ULVAC Co., Ltd | Kanagawa |
| Umeda Electric Co., Ltd | |
| UNBALANCE Corporation | Tokyo |
| Uneeds Corporation | |
| Unimedia, Inc. | Tokyo |
| UniqueLab, Inc. | |
| UNIRITA, Inc. | Tokyo |
| Unit.Com, Inc. | Osaka |
| United Immunity Co., Ltd | Tokyo |